1. Field of the Invention
The present invention relates to a storage apparatus and a control method therefor.
2. Description of the Related Art
There are known disk array devices that have a configuration in which housings, each of which accommodating a plurality of disk drives, are mounted in several layers. Such disk array devices are called “rackmount” disk array devices. Japanese Patent Application Laid-open Publication No. 2001-339853 discloses a power supply method for such a type of disk array device. According to the method disclosed, a power-supply apparatus is provided outside the housing and connected to a basic housing and an extension housing by dedicated control lines for controlling power supplied to the housings in such a way that the power supplied to the extension housing is turned ON/OFF in an interlocked manner with the ON/OFF of the power supplied to the basic housing.
In such a disk array device, the power-supply apparatus must be provided outside the housing and, in addition, it is necessary to provide dedicated control lines therefor. For this reason, problems in miniaturization and cost arise. In order to solve these problems, another type of a disk array device is known in which only a minimum number of cables are provided as wires for mutually connecting the housings and those cables are used for transmitting read data and write data as well as for exchanging a variety of control signals. In addition, some of the disk array devices, which have a minimum number of cables as described above, are capable of keeping some of the components in the extension housings ON even while the power of the disk drives in the basic housing is OFF. Then, when the operation of the disk drives in the basic housing is started, the extension housings recognize that the disk drives in the basic housing have started to operate, and start to fully operate as well.
In a disk array device having such a configuration, while the power supplied to the disk drives of the basic housing is in an OFF state, in the extension housings, only the components required to recognize the start of the operation in the basic housing are kept ON. That is, the operation state of the extension housings is different from that of when the extension housings are ON. For example, the amount of heat dissipated by the various devices mounted on the extension housings when only the components for start recognition are operated is smaller than the amount of heat dissipated when the power of the extension housings is ON. Therefore, from power-saving and noise-reduction points of view, it is preferable to make peripheral devices mounted on the basic housing, such as cooling fans, to operate in a state that is appropriate to cool the dissipated heat.